As it stands, gold and recruitable people are apparently limitless pools.
An army contained within the walls of a besieged city can continue to work
and entertain (ie. produce gold). They can also continue to recruit and/or
impress more men into their units. This makes besieging a pointless
strategic maneuver. It is also very counterintuitive.

I feel that both the amount of gold and the number of available people
should be fixed pools.

The population of an area should reflect the number of people available for
recruiting. The population can increase slowly by having a reproduction rate
and more quickly by having people from other areas migrate into the area.

The amount of gold in any given area should be:
= amount brought into the area by players
+ amount representing the pool of gold controlled by the market
+ amount in the pockets of the general populace

Units of farmers (or part of the general populace) can work on the land
to increase it's productivity and harvest the crops. Some excess can
be stored. The crops, farmers and stored food become potential assets
as well as potential targets for raids or attacks by the enemy. The landowner
becomes the protectorate of the lands (as was the case during the Middle Ages)
and a Feudalistic society is born!